An effector is a tool holder fixed to the end of a robot arm and which supports at least one tool configured to perform an operation on a workpiece, such as, for example, a machine tool.
As the robot does not have a rigid structure, according to one embodiment, the effector comprises a contact surface configured to bear against the workpiece near the tool.
In order to guarantee good machining quality, it is necessary to guarantee good rigidity between the contact surface of the effector and the workpiece that is to be machined. In addition, during machining, the contact surface of the effector must not move relative to the workpiece that is to be machined. If it does, and if the machine tool slips on the surface of the workpiece that is to be machined, it generates unacceptable machining marks. Finally, the contact surface must not damage the workpiece that is to be machined.
According to a first alternative form, the contact surface made of steel is smooth, hard, and has a shape configured to conform to the shapes of the workpiece that is to be machined. According to this first alternative form, the contact pressures are spread over the entire contact surface area, and this avoids marking the workpiece with an imprint. In addition, it guarantees good relative rigidity between the contact surface of the effector and the workpiece that is to be machined. However, this first alternative form is not entirely satisfactory because the contact surface of the effector has a low adhesion coefficient of the order of 0.2. Thus, the risks of the contact surface of the effector slipping on the workpiece that is to be machined are not negligible.
In order to avoid the tool slipping with respect to the workpiece that is to be machined, one solution is to degrade the cutting conditions in order to reduce the loads liable to cause slippage. However, this solution is not satisfactory because it reduces productivity.
According to a second alternative form, the contact surface is coated with fine very hard particles in order to increase the roughness of the contact surface and the coefficient of adhesion between the contact surface of the effector and the workpiece that is to be machined. As before, this second alternative form makes it possible to guarantee good relative rigidity between the contact surface of the effector and the workpiece that is to be machined. However, it is not entirely satisfactory because it is not possible to ensure that the slight penetration of the fine particles of the contact surface of the effector will not impair the workpiece that is to be machined.
According to a third alternative form, the contact surface comprises an elastomer coating in order to increase the adhesion coefficient. This third alternative form makes it possible to ensure a good adhesion coefficient, while at the same time guaranteeing the integrity of the workpiece that is to be machined. However, it is not entirely satisfactory because if the elastomer coating has a small thickness of the order of 0.01 mm, the risks of separation of the coating are high because of the shear stresses, and if the elastomer coating has a thickness greater than 0.01 mm it does not provide rigid contact between the contact surface of the effector and the workpiece that is to be machined because of its thickness combined with the softness of the material.